Though common in desert environments in the higher latitudes, the sand dunes of Ilocos Norte stands out as a unique land form in the Philippine setting. The dunes cover an area of about 85 sq kms, and stretch for at least 40 kms. Along the coast, sparse vegetation consisting mainly of grasses and shrubs blanket the low-relief area which is believed to have been formed a few thousand years ago through the combined action of wind, waves and shore currents. The marker embodying the declaration of the sand dunes as National Geological Monument was unveiled at Barangay Calayab, Laoag City on November 26, 1993.